1. Field of the Invention
The present invention generally relates to a load control system for controlling a plurality of processes, and more particularly a load control system included in a switching system, such as an exchange system having a plurality of processes for incoming calls.
2. Description of the Prior Art
FIG. 1 is a graph showing how incoming calls are regulated by a conventional load control system of an exchange system shown in FIG. 2A. The horizontal axis of the graph of FIG. 1 represents the number of incoming calls, and the vertical axis thereof represents the rate of accepted calls to the incoming calls. FIG. 2B is a flowchart showing the operation of the conventional load control system shown in FIG. 2A.
The conventional load control system has two types of processes for incoming calls, one of which is a call acceptance process, and the other one of which is a call regulation process. A call processing unit 2 of a processing unit 1 shown in FIG. 2A receives an incoming call received from a calling station or a called station in step S1 shown in FIG. 2B. In step S2, the call processing unit 2 increments the value of a counter for counting the number of incoming calls by 1. The call processing unit 2 receives data indicative of a call regulation rate from a regulation processing unit 3 of the processing unit 1, and determines, in step S3, whether or not the received call should be accepted by referring to the call regulation rate data.
In step S6, a load state monitoring unit 4 of the exchange system periodically monitors the state of a system load which shows, for example, how frequently the processing unit 1 of the exchange system is used for processing incoming calls. The load state monitoring unit 4 is externally provided with a parameter A representing an upper load limit, while the unit 4 periodically reads data indicating the system load state in step S7. In step S8, the load state monitoring unit 4 compares the upper load limit with the data indicating the system load state, and determines whether or not the processing unit 1 has an overload. When it is determined that the processing unit 1 is operating with a normal, the process ends. When it is determined, in step S8, that the processing unit 1 has an overload, the load state monitoring unit 4 updates, in step S9, the call regulation rate to be used in the next cycle. In step S3, the updated call regulation rate is used when the next incoming call is processed.
Referring to FIG. 1, the call regulation process is started when the number of incoming calls has reached a point "a", and all incoming calls are regulated (not accepted) when the number of incoming calls has reached a point "b". The number of accepted calls is gradually decreased as the number of incoming calls increases between the points "a" and "b" When the number of incoming calls exceeds the point "b", the call acceptance process is not carried out at all. This substantially degrades the communications services.